What i have been doing for years now is to setup Thunderbird leveraging maildir...Now, the majority of the time i do read my mail via google's webmail...but on occasion i do use Thunderbird for reading mail. But the benefit of having my mail locally accessible - as indivudual files under maildir - is that things are snappier for going through all of my messages...But the secondary benefit is that i can (and have been for years) backing up my email as files...In essence all the files under thunderbird's maildir can be copied/pasted to some other storage place/folder/network share/whatever...so i get speed and protection! Plus this (having all my email messages locally-accessible) makes it trivially easy to "re-import" (if you want to call it that) my email from GSuite over to any other IMAP-capable mail provider...it is as easy as dragging files from my GSuite-account in thunderbird over to the other, non-GSuite account within said same Thunderbird view. (Granted it takes time to push up email to the new provider this way if you have tons of messages...but its easy.) I'm sure there are more efficient methods to get your messages from Goolgle and shifted over to another mail provider...but this is what i've done, and it works. YMMV depending on the number of messages you're dealing with, and any constraints your new/other mail provider might have in receiving loads of "new" messages.